A neomycin resistance cassette with one loxP site was inserted into intron 3, and a second loxP site was introduced into intron 2. In addition, a FRT-flanked neomycin cassette was inserted. Flp-mediated recombination removed the FRT-flanked neo cassette. Deletion of exon 3 via Cre-mediated recombination will result in a frame-shift mutation. (J:99813)